Crushers, shredders, hammer mills, ring mills, and the like, are often used to process scrap material and stone, to crush or reduce the size of the material so that it can more easily be handled by other equipment for further processing or use.
Such crushers typically include a plurality of hammers mounted about a rotatable shaft. As the shaft rotates, the hammers engage and crush whatever media is introduced into the crusher. The hammers can be mounted between spiders which are positionally fixed relative to the rotor shaft. Typically, the rotor shaft is cylindrical. The use of a cylindrical shaft requires that the spider arms be positively keyed to the shaft, for example, using a square or rectangular key on the spider and a corresponding keyway on the shaft, so that the spider arms cannot rotate relative to the shaft. The use of a keyway weakens the main shaft and makes removal of the spiders and end discs a much more difficult task. Further, the key will weaken over time, and eventually the rotor assembly will shift between the shredder housings. Obviously, this can necessitate a repair of the crusher, requiring that operation of the crusher be stopped for the duration of the repair. Depending on the location of the spider which is no longer positively fixed with respect to the shaft, the crusher can be shut down for a considerable period of time.
A shredder, crusher, hammermill, ringmill or the like is provided with a multi-sided rotor shaft to which spider arms and hammers are mounted. The rotor shaft has at least at least one pair, and preferably two or more pairs, of opposing sides. The hammers are pivotally mounted between spider arms. The spider arms have bases which include openings. The spider arm base openings have straight sides corresponding to the number of straight sides on the rotor shaft. The spider arm straight sides engage the rotor shaft straight sides. Hence, the spider arms are rotationally fixed in place relative to the rotor shaft without the of a central key, or other types of fasteners, allowing for easier assembly and reduced maintenance costs for the shredder.